Do you hear a grinding or scraping noise coming from your car’s undercarriage while driving? Not only is the sound annoying, but it can also indicate a problem that compromises overall vehicle safety. You’ll want to find out what’s causing the noise so that you can fix the issue right away.
What Causes a Grinding Noise When Driving? 4 Common Causes
Unfortunately, there isn’t a one-size-fits-all answer as to why you might be hearing a grinding noise from your car’s undercarriage while driving. To determine the root cause of the concern, you (or your mechanic) will need to do some troubleshooting.
Once you start to dig in, there’s a good chance you’ll find the noise coming from one of the following sources.
Worn Brake Pads or Shoes
Brake pads and shoes help create the friction needed to bring your car to a stop. In a disc brake system, the pads are pressed against a disc-shaped rotor to halt the vehicle. When a drum brake system is used, shoes are pushed outward against a circular drum to create the same effect.
Severely worn brake pads or shoes can create a grinding noise while driving. The problem happens when the brakes are worn down to the backing plates (or wear indicators), allowing for constant contact with the drum or rotor.
Rusted Rotors
When a vehicle sits for an extended period, the surface of the rotors will accumulate rust. The rust can cause the brakes to make a grinding noise whenever the car is in motion. Usually, the noise goes away quickly, as the rust gets cleared off by the brake pads each time the brakes are applied.
Bent Backing Plate
Drum and disc brake systems both use backing plates. The backing plates are located behind the brakes to shield the braking components from water and debris. In a drum brake system, each backing plate also provides a mounting point for the brake shoes and related components.
Because backing plates are made of thin metal, they can easily get bent. When that happens, the backing plate then contacts the rotor (in a disc brake system), creating a grinding noise. It’s also possible for the backing plate to contact the drum in a drum brake system, though the issue is far less common.
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I have a grinding noise coming from my front left wheel. It’s there when I accelerate, getting louder as speed increases. [It’s] a little louder when turning, and gets the loudest when I’m braking. I’ve done a lot of research to pinpoint the issue before paying for service, but I’m stuck between bad rotors/brake pads and bad wheel bearings. It’s a ‘09 Chevy Impala LTZ.
Bad Wheel Bearing
Your car has a wheel bearing (or axle bearing) at each wheel. Each wheel bearing allows one of the wheels to rotate with minimal friction. The wheel bearings also help support the weight of the vehicle.